[shang]

Dear foamers,

Does anybody know how to extract data along a line from the sampled surface.

I can sample the plane for each time step, but I don't know how to sample a line from these planes. It seems the OpenFOAM's line sampling tool (singleGraph) only works for the data in the written-out time directories which is for the whole flow domain.

Anybody has any hint or solution?

Kind regards,
Yeru

[clapointe]

You can extract data along a line using the sample utility. Examples are provided in the sampleDict here : https://github.com/OpenFOAM/OpenFOAM...tem/sampleDict.

Caelan

[shang]

Hi Caelan,

Thanks for that. But it is not what I want. Maybe I didn't explain myself clearly...

I know sample utility can sample line and surfaces. But I can only know which line I want to look into after the simulation. So what I am doing is to sample the most important surfaces/planes for each time step (they will be stored in directory "postProcessing" in various format, e.g. raw, vtk and foamFile). Then when I know which line to be analysed, I will (if I can) sample the line data from the stored sampled planes. This would save me from running my calculation again which would normally take 1 week or 2 since it is LES.

Do you know any way of doing that?

Many thanks,
Yeru

[clapointe]

Do you mean that you are only keeping the 2d slices and getting rid of the rest of the data? If so, I misunderstood. If you have a uniform grid, post processing in matlab or python is pretty straightforward. Otherwise I think paraview would be able to open vtk files for further analysis.

Caelan

[shang]

Yes, only 2D slices. Sorry for confusing you.

My grid is not uniform. So I suppose I need creating an uniform grid in Matlab then mapping my 2D slice's result onto it. I am currently exploring this option, but not sure how big the effect of various interpolation procedures on the result. (from cell centre value in OpenFOAM -> point value on the sampled 2D slices -> point value in Matlab with different grid -> sample a line in Matlab). Therefore, I still prefer to use OpenFOAM or ParaView to do this job. But I will let you know if Matlab works well in this case.

I tried to use ParaView to visualise the 2D slice, it can show the contour and do line sampling. But it can only process a single vtk file for each time and I have to do it manually. So If I want to see how my flow field goes and process multiple vtk files, do you know how can I do it?

Thanks,
Yeru

[clapointe]

You can compile Paraview with python capability -- then you can write a python script that iteratively loads/processes a vtk file.

Caelan

[shang]

Hey Caelan,

Sorry for my late response. I am pretty new to Python, any idea where I can start or if there is any existing code I can borrow?

Thanks,
Yeru

[clapointe]

This is a great resource for OpenFOAM : https://holzmann-cfd.com/community/t...ost-processing -- you should be able to find some example scripts for paraview as part of the blender tutorials.

Caelan

[shang]

Thanks Caelan, I will have a look!